A review and critical evaluation of the literature on the assessment and assurance of the quality of medical care, including the appropriateness of use of service. There will be emphasis on: concepts of quality; the comparison of alternative approaches to assessment; methodological issues in measurement; factors associated with levels of performance; the implementation of quality assurance systems in medical care programs and their impact, including costs and desired as well as undesired effects. There will be special attention to public policy issues and to identifying fruitful directions for further research and development.